Conventionally, one type of printing device is provided with a thermal head on which a plurality of heat generating elements are arranged vertically in a line. The thermal head is moved in a direction orthogonal to the aligned direction of the heat generating elements, by means of a pulse motor, with respect to a sheet on which printing is to be applied. While the thermal head is being moved with respect to the sheet, a selected number (or-all) of the heat generating elements are applied with a pulse-like voltage that energizes them. Thus, dot pattern images can be printed on a heat sensitive sheet, or by transferring ink from a thermal ink ribbon to a sheet. Pulse motors are generally employed as the driving means for driving the head since the driving amount can be controlled accurately. Intervals (spaces) between the printed dots in the horizontal direction are determined by the driving amount. The pulse motor is usually driven in an open loop circuit, and therefore, even in normal conditions, it generates torque to satisfy a maximum load condition. Therefore more energy than necessary is always required, and thus the pulse motor greatly increases the power consumption of the device. This is an important consideration especially in a battery powered printer.
However, in a tape printing device, the printing head remains stationary and the recording medium or tape is fed, by a driving mechanism which also employs a pulse motor. As a result the same power consumption problems as mentioned above will occur.
Recently, to rectify the power consumption problem mentioned above, a DC servo motor provided with an optical encoder or the like for detecting the rotation angle of the motor has been employed. However, the DC servo motor utilizes a feedback control system which thus increases the cost and complexity of the printing device.